Establishment And Source Analysis Of VOCs Source List In A Typical Coastal City

Since the promulgation of the Ten Atmospheric Regulations,after several years of efforts,the concentration of PM2.5 in China’s ambient air has shown a significant downward trend,while the ozone pollution has been increasing year by year.Surface ozone is produced by photochemistry of nitrogen oxides(NOx)and volatile organic compounds(VOCs).The formation rate and concentration are mainly affected by the concentration of precursors such as NOx,VOCs and CO and meteorological conditions.As a major air pollutant,ozone can do harm to human health and terrestrial ecosystem.In urban areas of China,ozone often becomes the primary air pollutant in summer.Through the analysis of air quality in Weihai in recent years,it was found that ozone concentration in Weihai increased gradually from 2016 to 2018.Different from other cities in China,the remarkable characteristics of Weihai ozone change are that the spring concentration is higher than that of the mainland,and the summer concentration is lower than that of the mainland.However,the study on the source of ozone in Weihai has not been reported yet.It is clear that the pollution characteristics and sources of VOCs and NOx,which are important precursors of ozone,have become the key issues in ozone pollution control.At the same time,in the current severe situation of atmospheric combined pollution,more effective measures are needed to control the emission of nitrogen oxides and volatile organic compounds in order to effectively control ozone pollution and offset the increase of ozone caused by the reduction of particulate matter,thus achieving a win-win situation of haze control and ozone control.The main contents of this study:(1)Taking 2017 as the base year,adopting "bottom-up" as the main method and "top-down" as the supplementary method to establish a reliable VOCs emission from Weihai City.(2)Two representative monitoring sites(Shandong University Weihai Campus and Port Administrator Committee)were selected to conduct VOCs sampling and analysis in January,March,May,June and September 2018.The pollution characteristics and pollution levels of volatile organic compounds(VOCs)were analyzed by using the PMF model to analyze the source of monitoring data.The main VOCs emission sources near two monitoring sites in Weihai City were analyzed.The main conclusions are as follows:(1)In 2017,the VOCs emission of the main air pollutants in Weihai City was 35.5 million t/a(excluding 28.7 million t/a of fishing vessels).The results showed that mobile sources,solvent sources and process sources were the main sources of VOCs,accounting for 36.7%,32.7% and 15.7% of the total VOCs emissions,respectively.Rongcheng,Wendeng and Rushan contributed the most to VOCs emissions,accounting for 38.9%,21.3% and 13.0% of the total VOCs emissions,respectively(including fishing boats).Rongcheng,Wendeng and Rushan contributed the most to VOCs emissions.In Shan City,the proportion of total emissions was 39.6%,25.5% and 15.3% respectively(excluding fishing vessels).(2)Based on the data of VOCs detection and analysis in 2018,it is found that the main VOCs species in the air of two monitoring sites in Weihai City are similar to those in the air of woodworking machinery in Lingang.In terms of VOCs-PAMS,the concentration of VOCs in monitoring sites of Shanda University was the highest in January,the lowest in June,and the trend was June < May < March < September < January.The concentration of VOCs in monitoring sites near port was similar to that in Shanda monitoring sites,and the trend was June < May < September < January.The diurnal variation characteristics of VOCs components in two monitoring sites were analyzed.The highest hourly concentration appeared at 7:00 in the morning and the lowest value appeared at 11:00 in the noon.The diurnal variation of VOCs emissions in the two monitoring sites was also related to the diurnal variation of vehicle exhaust,industrial production and daily life.The analysis of VOCs components identified 11 VOCs target compounds with the highest contents of propane(Propane),ethane(Ethane),dodecane(Dodecane),isopentane(Isobutane),ethylene(Ethylene),acetylene(Acetylene),n-pentane(n-Pentane),n-Butane(n-Butane),toluene(Toluene)and benzene(Benzene).The top ten VOCs in VOCs are ethylene,toluene,propylene,propane,isopentane,n-butane,isoprene,ethane,m-xylene and isobutane.For Shanda Campus and port-vicinity monitoring sites,the VOCs volume concentration and ozone generation potential in the atmosphere at 7:00 am are higher than those at 11:00 am due to the influence of VOCs reaction activity and atmospheric diffusion conditions(3)The results of PFM model analysis of VOCs at Shanda and Lingang monitoring points show that there are four factors in the monitoring points of the University of Shanda,among which the oil and gas volatilization source accounts for the highest proportion,reaching 28.9%,followed by LPG/NG emission sources,28.5%,solvent use sources,21.3% and mobile sources;four factors have been identified at Lingang woodworking machinery monitoring points,and the source of process is VOCs-PAMS.The highest contribution was made by rubber products industry and chemical industry,accounting for 65.9%,motor vehicle exhaust 20.9% and oil and gas volatile 13.1%.The main sources of PMF analysis results include mobile sources,process sources,oil and gas volatilization sources,solvent use sources and LPG/NG emission sources.